Spread spectrum applications of universal frequency translation

Abstract

Frequency translation and spread spectrum applications of same are described herein. Such applications include, but are not limited to, unified down-conversion and de-spreading, unified up-conversion and spreading, RAKE receivers utilizing unified down-conversion and de-spreading, and Early/Late receivers utilizing unified down-conversion and de-spreading, and combinations and applications of same. Additionally, applications are included for limiting spectral growth during unified up-conversion and spreading of a baseband signal.

What is claimed is: 
     
       1. A system for down-converting and de-spreading a spread spectrum signal, comprising:
 a first module configured to generate a spreading code corresponding to the spread spectrum signal; 
 a second module configured to generate a control signal that comprises said spreading code; and 
 a third module configured to sample said spread spectrum signal and store said samples, said third module controlled at least in part by said control signal, so as to down-convert and de-spread said spread spectrum signal to obtain a de-spread baseband signal; 
 wherein said third module comprises a storage device coupled to a switch to store said samples, wherein successive samples form said de-spread baseband signal; and 
 wherein said storage device integrates energy over multiple half-cycles of said spread spectrum signal as a function of said control signal. 
 
     
     
       2. The system of  claim 1 , further comprising a fourth module configured to generate an oscillating signal. 
     
     
       3. The system of  claim 2 , further comprising a fifth module configured to modulate the oscillating signal with the spreading code to generate a spread oscillating signal. 
     
     
       4. The system of  claim 3 , further comprising a sixth module configured to convert said spread oscillating signal into said control signal that comprises a plurality of pulses. 
     
     
       5. The system of  claim 4 , wherein a pulse width of a pulse of said control signal is non-negligible. 
     
     
       6. The system of  claim 4 , wherein a pulse width of a pulse of said control signal is negligible. 
     
     
       7. The system of  claim 4 , wherein a pulse width of a pulse of said control signal is any fraction of a center frequency of a baseband of said spread spectrum signal. 
     
     
       8. The system of  claim 4 , wherein a frequency of said control signal is based at least in part on a frequency of said spread oscillating signal. 
     
     
       9. The system of  claim 1 , wherein said control signal is a harmonic or sub-harmonic of said spread spectrum signal. 
     
     
       10. The system of  claim 1 , wherein said third module comprises a switch controlled by said control signal to under-sample the spread spectrum signal, resulting in under-samples. 
     
     
       11. The system of  claim 10 , wherein said switch is a transistor. 
     
     
       12. The system of  claim 1 , wherein said storage device is a capacitor. 
     
     
       13. The system of  claim 1 , wherein a center frequency of said control signal is approximately equal to a center frequency of said spread spectrum signal. 
     
     
       14. The system of  claim 1 , wherein a center frequency of said control signal is above a baseband frequency of said spread spectrum signal. 
     
     
       15. The system of  claim 1 , wherein sampling comprises transferring charge from said spread spectrum signal. 
     
     
       16. The system of  claim 1 , wherein the spread spectrum signal is directly down-converted and de-spread to obtain a de-spread baseband signal. 
     
     
       17. The system of  claim 16 , wherein directly down-converting said spread spectrum signal to a de-spread baseband signal eliminates use of front-end mixers, front-end radio frequency amplification circuitry and intermediate frequency conversion circuitry. 
     
     
       18. A system to down-convert and de-spread a spread spectrum signal, comprising:
 a first circuit configured to modulate an oscillating signal based on a spreading code, and to generate a control signal that comprises a plurality of pulses; and 
 a second circuit configured to transfer charge from said spread spectrum signal and integrate said charge over multiple cycles of said spread spectrum signal as a function of said control signal; 
 wherein the second circuit comprises a switch controlled by said control signal to under-sample the spread spectrum signal, resulting in under-samples. 
 
     
     
       19. The system of  claim 18 , wherein a frequency of said control signal is a harmonic or sub-harmonic of said spread spectrum signal. 
     
     
       20. The system of  claim 18 , further comprising a third circuit for generating an oscillating signal. 
     
     
       21. The system of  claim 18 , wherein a frequency of said control signal is based at least in part on a frequency of said oscillating signal. 
     
     
       22. The system of  claim 18 , wherein said control signal is a harmonic or sub-harmonic of said spread spectrum signal. 
     
     
       23. The system of  claim 18 , wherein said switch is a transistor. 
     
     
       24. The system of  claim 18 , wherein a center frequency of said control signal is approximately equal to a center frequency of said spread spectrum signal. 
     
     
       25. The system of  claim 18 , wherein a center frequency of said control signal is above a baseband frequency of said spread spectrum signal. 
     
     
       26. The system of  claim 18 , wherein the spread spectrum signal is directly down-converted and de-spread to obtain a de-spread baseband signal. 
     
     
       27. The system of  claim 26 , wherein directly down-converting said spread spectrum signal to a de-spread baseband signal eliminates use of front-end mixers, front-end radio frequency amplification circuitry and intermediate frequency conversion circuitry. 
     
     
       28. A system to down-convert and de-spread a spread spectrum signal, comprising:
 a first circuit configured to modulate an oscillating signal based on a spreading code, and to generate a control signal that comprises a plurality of pulses; and 
 a second circuit configured to transfer charge from said spread spectrum signal and integrate said charge over multiple cycles of said spread spectrum signal as a function of said control signal; 
 wherein the second circuit further comprises a storage device coupled to a switch to store said charge, wherein successive samples of said charge form said de-spread baseband signal. 
 
     
     
       29. The system of  claim 28 , wherein said storage device is a capacitor.